Quantum vortices

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Definition: Quantum vortex

In physics, a quantum vortex is a topological defect exhibited in superfluids and superconductors. The existence of these quantum vortices was independently predicted by Richard Feynman[1] and Alexei Alexeyevich Abrikosov[2] in the 1950s. They were later observed experimentally in Type-II superconductors, liquid helium, and atomic gases (see Bose-Einstein condensate).

A quantum vortex in a superfluid is different to one in a superconductor. The key similarity is that they are both topological defects, and they are both quantized. In addition, the make up of each quantum vortex is neither superfluid nor superconductor, for each system. In a superfluid, a quantum vortex "carries" the angular momentum, thus allowing the superfluid to rotate; in a superconductor, the vortex carries the magnetic flux.

Source: Wikipedia.org  http://en.wikipedia.org/wiki/Quantum_vortex


Half-quantum vortices

By Physics Today on January 27, 2011 11:54 AM

In most known superconductors, electrons pair up to form spin singlets: combinations of spin up and spin down with zero angular momentum. But in a few materials, including strontium ruthenate (Sr2RuO4, or SRO), the electron pairs form spin triplets (see the article by Yoshiteru Maeno, Maurice Rice, and Manfred Sigrist in Physics Today, January 2001, page 42). JM300.jpg In SRO, the triplets are thought to take a form that can be represented as two weakly interacting superfluid condensates: one of spin-up pairs, the other of spin-down pairs. That arrangement can support half-quantum vortices (HQVs), in which one condensate has one more quantum of vorticity than the other. Because of HQVs' potential applications to quantum computing, they’ve been extensively studied by theorists and sought by experimentalists. Now, researchers led by Raffi Budakian (University of Illinois at Urbana-Champaign) have found the first experimental evidence of HQVs in SRO.
More: http://blogs.physicstoday.org/update/2011/01/half-quantum-vortices-1.html

Multivalued Fields in Condensed Matter, Electromagnetism, and Gravitation

Hagen Kleinert, Professor of Physics, Freie Universit¨at Berlin (Germany)
URL: http://users.physik.fu-berlin.de/~kleinert/public_html/kleiner_reb11/psfiles/mvf.pdf